Heat dissipation, thermal stresses and cost are key light-emitting diode (LED) packaging issues. Heat dissipation limits
power levels. Thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric
printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most
traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20th
century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. An OIDA
LED workshop cited a need for better thermal materials. There are an increasing number of low-CTE materials with
thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other low-CTE
materials with lower thermal conductivities. Some of these materials are low cost. Others have the potential to be low
cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing
the number of required LEDs. Advanced thermal materials can constrain PCB CTE and greatly increase thermal
conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The
latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status,
applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites
reinforced with carbon nanotubes and other thermally conductive materials.